AB0895 SUBCUTANEOUS IMMUNOGLOBULINS IN IDIOPATHIC INFLAMMATORY MYOPATHIES: IS IT TIME FOR A THERAPY DISCONTINUATION SCHEDULE?
Authors: C. Cardelli, S. Barsotti, E. Laurino, M. Diomedi, F. Fattorini, A. Tripoli, L. Carli, M. Mosca
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Subcutaneous immunoglobulins (SCIg) therapy is effective in patients with Idiopathic Inflammatory Myopathies (IIMs), especially in severe and refractory forms of the disease; however, its use is burdened by high costs. Although it is now known that the dosage to be used for the immunomodulatory effect is 2 g/kg per month, there are no standardised tapering or discontinuation schemes to date. <h3>Objectives</h3> The aim of the study was to assess whether there are differences in terms of clinical outcomes and patient Quality of Life (QoL) between two different SCIg treatment regimens, involving discontinuation of therapy after the first six months or continuation of the drug for a further six months. <h3>Methods</h3> Within the cohort of IIM patients (2017 EULAR/ACR criteria) followed at our Myositis Clinic, we selected those who were treated with SCIg and, dividing them into two groups according to whether they discontinued therapy after the first six months, we performed a retrospective analysis on data prospectively collected. For each patient, demographic and clinical data (age, sex, disease subset and duration, organ involvement, comorbidities, treatment) were collected from medical charts. The International Myositis Assessment &amp; Clinical Studies Group Disease Activity Core Set Measures (IMACS-CSMs) [Physician Global Activity (PhGA), Patient Global Activity (PGA), 8-items Manual Muscle Testing (MMT8), Health Assessment Questionnaire (HAQ), serological muscle enzymes values] were used to assess the disease activity at baseline and to evaluate the clinical outcomes after six and twelve months from the start of SCIg therapy. Patients' perspective was evaluated also by administration of Patient Reported Outcomes (PROs) not included in the IMACS-CSMs: Short-Form 36 Items Health Survey (SF-36), Functional Assessment of Chronic Illness Therapy Fatigue Subscale (FACIT-F), Hospital Anxiety and Depression Scale (HADS). We then compared the delta of IMACS-CSMs and PROs between the 12-month (12m) and 6-month (6m) assessments to detect any significant changes in patients' health status following the discontinuation of SCIg therapy. <h3>Results</h3> We included 18 patients (12 dermatomyositis, 6 polymyositis; 61.1% female) with a mean age at the beginning of SCIg therapy of 63.8±14.8 years. Of these, 10 (55.6%) discontinued SCIg therapy after 6 months of treatment while 8 (44.4%) continued it for at least one year. We found no differences between the two groups in terms of disease activity and patients' QoL at baseline. At 12 months evaluation, there were no statistically significant differences in PhGA (2.9±1.7 vs 2.5±2.0), MMT8 (67.9±8.0 vs 75.1±6.1) and serum values of muscle enzymes (CPK, LDH, aldolase) between those who had discontinued SCIg after the first 6 months and those who continued the treatment. Patients' QoL was also found not to differ between the two groups, as no statistically significant differences emerged between the scores of HAQ, all SF-36 domains, FACIT-F and HADS anxiety and depression subscales. The delta 12m-6m of QoL assessment parameters showed no differences between the two groups, while there was a worsening of mean PhGA (1.5±1.4 vs -0.5±1.8, <i>p</i>=0.026) and MMT8 (-5.9±6.6 vs 3.3±2.8, <i>p</i>=0.010) in those who discontinued therapy compared with those who continued SCIg. <h3>Conclusion</h3> Although preliminary and with the limitations inherent to the retrospective nature of the study, these data seem to suggest that there are no significant differences in outcomes assessed by IMACS-CSMs and in patient's perception of the disease between different treatment regimens concerning the discontinuation of SCIg. If our findings will be confirmed by future studies on larger cohort of IIM patients, although it appears that there may be a slightly deterioration in muscle function, discontinuing SCIg therapy after the first six months of treatment could reduce health costs, without the risk of significantly compromising patients' quality of care. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.